Installation system for securing workpieces of composite materials and the like and threaded fastener for such system

• US 4,850,771 A
• Filed: 05/20/1988
• Issued: 07/25/1989
• Est. Priority Date: 04/01/1986
• Status: Expired due to Fees

• Current Assignee: Huck Patents, Inc.
• Original Assignee: Ramon L. Hurd
• Inventors: Hurd, Ramon L.
• Primary Examiner(s): Moon, Charlie T.
• Application Number:
  US07/196,881
• Time in Patent Office: 431 Days
• Field of Search: 411/39, 411/40, 411/36, 411/41, 411/43, 411/55, 411/367, 411/360, 411/361, 403/408, 29/240, 29/525.1, 29/523
• US Class Current: 411/43
• CPC Class Codes: F16B 29/00 Screwed connection with deformation of nut or auxiliary member while fastening Nuts fastened to surfaces by riveting F16B37/065; members deformed for locking screws, bolts or nuts F16B39/22
• CPC Class Codes: F16B 4/004 Press fits, force fits, interference fits, i.e. fits without heat or chemical treatment F16B4/002 takes precedence
• CPC Class Codes: F16B 5/01 by means of fastening elements specially adapted for honeycomb panels
• CPC Class Codes: Y10S 411/999 with retainer, e.g. tether
• CPC Class Codes: Y10T 29/4994 Radially expanding internal tube
• CPC Class Codes: Y10T 29/49945 by driven force fit
• CPC Class Codes: Y10T 29/49952 At least one part is nonmetallic
• CPC Class Codes: Y10T 403/75 having a joining piece extending through aligned openings in plural members

Abstract

An installation system for securing workpieces of composite type materials and including a fastener adapted to be located in aligned bores in such workpieces with a preselected interference fit, with the fastener comprising a pin having an elongated shank, an enlarged head and enlarged diameter smooth shank section adjacent the pin head, and further having a threaded section extending from the smooth shank section to a breakneck groove located in the shank to define a frangible portion at its free end, the breakneck groove adapted to fracture at a preselected axial load of generally low magnitude, a thin gauged expansion sleeve having an inside diameter less than the diameter of the smooth shank section, the sleeve having an outside diameter permitting the assembly of the sleeve into the workpiece bores with a snug fit, the breakneck groove having an axial strength at least equal to the maximum axial load required to pull the pin member fully into the sleeve with the smooth pin shank section expanding the sleeve into the workpiece bores to provide the preselected interference fit, the breakneck groove having an axial strength no greater than a preselected low percentage greater than the axial load whereby the frangible portion of the shank can be severed at a minimal axial load applying a member to the frangible portion to pull the pin member into the sleeve and then severing the frangible portion separately from the final installation of the fastener.

Claims

1. A fastener for securing together a plurality of workpieces of a composite type material and adapted to be located in aligned bores in such workpieces with a preselected interference fit and with the fastener adapted to secure such workpieces varying in total thickness from a preselected maximum to a preselected minimum total thickness, said fastener comprising:

a pin member having an elongated shank and an enlarged head at one end,

said pin member having an enlarged diameter smooth shank section adjacent said pin head,

said pin member having a threaded section extending generally from said smooth shank section to the opposite end of said pin member,

a breakneck groove section located within said threaded section to define a frangible portion at the free end of said threaded section,

said breakneck groove section being the weakest section of said pin member and adapted to fracture at the preselected load of generally low magnitude, said threaded pin section having a maximum diameter less than the diameter of said smooth shank section,

a thin gauged expansion sleeve having a tubular portion with an enlarged annular flange at one end,

said sleeve having an inside diameter greater than said maximum diameter of said threaded pin section and less than the diameter of said smooth shank section;

said tubular portion of said sleeve having a length no less than around the maximum total thickness of the workpieces, and having an outside diameter permitting assembly of said sleeve, with said pin member attached, into the workpiece bores,

a nut member having a threaded nut section at one end and an enlarged head portion at its opposite end, said enlarged head portion having an enlarged counterbore having a diameter greater than the outside diameter of said tubular portion of said sleeve, said counterbore having an axial depth at least equal to the maximum extension of said sleeve tubular portion beyond the workpieces for workpieces of minimum total thickness, said threaded nut section having a preselected axial length, said frangible portion of said threaded section having an axial length no less than around one half of the axial length of said threaded nut section, said nut member having a preselected overall axial height,

said pin member having the length of that portion of said pin shank from said pin head to said breakneck groove section being no greater than around the sum of the maximum total thickness of the workpieces, said preselected height of said nut member and the thickness of said sleeve flange,

said threaded pin section being continuously threaded over its full length whereby said nut member can be threaded onto said threaded pin section and across said breakneck groove section past said frangible portion and onto that portion of said threaded section on the pin head side of said breakneck groove section,

said frangible portion having a thread form adapted to be threadably gripped for applying a relative axial, pulling force between said pin member and said sleeve,

said breakneck groove section having an axial strength at least equal to the maximum axial load required to pull said pin member fully into said sleeve with said smooth pin shank section expanding said sleeve into the workpiece bores to provide the preselected interference fit, the axial strength of said breakneck groove section being no greater than around twenty percent (20) greater than said maximum axial load whereby said frangible portion of said shank can be severed from said shank at a minimum axial load, and

a flat washer means having a clearance fit on the end of the sleeve for engagement with the exposed face of the workpiece assembly, whereby the workpiece assembly faces are captively retained between the washer means and sleeve flange,

said sleeve flange and flat washer means being adapted to non-rotatably engage the exposed faces of the workpiece assembly while the pin is being drawn into the sleeve, whereby said flange and washer inhibit delamination of the workpiece composite materials,

said nut member being adapted to be torqued onto said pin member to pull said member into said sleeve to cause said radial expansion and to be continued to be torqued to apply the final desired clamp load.

2. A fastener for securing together a plurality of workpieces of a composite type material and adapted to be located in aligned bores in such workpieces with a preselected interference fit and with the fastener adapted to secure such workpieces varying in total thickness from a preselected maximum to a preselected minimum total thickness, said fastener comprising:

a pin member having an elongated shank and an enlarged head at one end,

said pin member having an enlarged diameter smooth shank section adjacent said pin head,

said pin member having a threaded section extending generally from said smooth shank section to the opposite end of said pin member,

a breakneck groove section located within said threaded section to define a frangible portion at the free end of said threaded section,

said breakneck groove section being the weakest section of said pin member and adapted to fracture at a preselected load of generally low magnitude,

said threaded pin section having a maximum diameter less than the diameter of said smooth shank section,

a thin gauged expansion sleeve having a tubular portion with an enlarged annular flange at one end,

said sleeve having an inside diameter greater than said maximum diameter of said threaded pin section and less than the diameter of said smooth shank section,

said tubular portion of said sleeve having a length no less than around the maximum total thickness of the workpieces, and having an outside diameter permitting assembly of said sleeve, with said pin member attached, into the workpiece bores,

a nut member having a threaded nut section at one end and an enlarged head portion at its opposite end, said enlarged head portion having an enlarged counterbore having a diameter greater than the outside diameter of said tubular portion of said sleeve, said counterbore having an axial depth at least equal to the maximum extension of said sleeve tubular portion beyond the workpieces for workpieces of minimum total thickness, said threaded nut section having a preselected axial length, said frangible portion of said threaded section having an axial length no less than around one half of the axial length of said threaded nut section, said nut member having a preselected overall axial height,

said pin member having the length of that portion of said pin shank from said pin head to said breakneck groove section being no greater than around the sum of the maximum total thickness of the workpieces, said preselected height of said nut member and the thickness of said sleeve flange,

said threaded nut section of said nut member having threads formed for threaded engagement onto that portion of said threaded section on the pin head side of said breakneck groove section,

said frangible portion having a thread form adapted to be threadably gripped for applying a relative axial, pulling force between said pin member and said sleeve,

said breakneck groove section having an axial strength at least equal to the maximum axial load required to pull said pin member fully into said sleeve with said smooth pin shank section expanding said sleeve into the workpiece bores to provide the preselected interference fit, said breakneck groove section having an axial strength no greater than around twenty percent (20%) greater than said maximum axial load whereby said frangible portion of said shank can be severed from said shank at a minimum axial load, and

a flat washer means having a clearance fit on the end of the sleeve for engagement with the exposed face of the workpiece assembly, whereby the workpiece assembly faces are captively retained between the washer means and sleeve flange,

said sleeve flange and flat washer means being adapted to non-rotatably engage the exposed faces of the workpiece assembly while the pin is being drawn into the sleeve, whereby said flange and washer inhibit delamination of the workpiece composite materials,

said nut member being adapted to be torqued onto said pin member to pull said pin member into said sleeve to cause said radial expansion and to be continued to be torqued to apply the final desired clamp load.

3. The fastener of claim 2 with said breakneck groove section having a tensile fracture load of no greater than around fifty percent (50%) of the final tensile load to be applied by said nut member at final clamp up thereby facilitating the removal of said frangible portion of said shank at said breakneck groove section at a minimum tensile load.

4. In association with a workpiece assembly comprising facially-engaged composite material workpieces having aligned holes therethrough defining an annular hole surface:

the improvement comprising a sleeve-expansion pin having an enlarged head, a smooth-surfaced shank section, and threaded shank section;

a freely-movable sleeve having a radial flange at one end, and a length that enables its other end to extend beyond an exposed face of the workpiece assembly when said sleeve is slidably inserted into the aligned holes in the workpiece assembly;

an annular flat washer having a clearance fit on the end of the sleeve and being in engagement with the exposed face of the workpiece assembly, whereby the workpiece assembly faces are captively retained between the washer and sleeve flange, and

a rotatable nut member threadable onto the threaded section of the pin to draw the pin into the sleeve;

the diameter of the smooth-surfaced shank section of the pin being slightly greater than the freely-movable sleeve internal diameter, whereby when the pin is drawn rectilinearly into the sleeve said sleeve is expanded into an interference fit with the annular hole surface;

said sleeve flange and said flat washer means being adapted to non-rotatably engage the exposed faces of the workpiece assembly while the pin is being drawn into the sleeve, whereby said flange and washer inhibit delamination of the workpiece composite material; and

a breakneck groove formed in the threaded section of the pin to define a breakneck groove section, whereby an exposed section of the pin can be removed after the pin has been fully drawn into the sleeve, the axial strength of said breakneck groove section being no greater than around twenty percent (20%) greater than said maximum axial load twenty said frangible portion of said shank can be severed from said shank at a minimum axial load.